Power-on reset circuit with supply voltage and temperature immunity, ultra-low DC leakage current, and fast power crash reaction

Abstract

A power-on reset circuit includes a Schmitt trigger circuit, a voltage divider, and a compensate circuit. The Schmitt trigger circuit includes a plurality of MOS devices of a uniform threshold voltage (Vt) for determining a power reset trigger level. The voltage divider is coupled to an input of the Schmitt trigger circuit for tracking the supply signal. The compensate circuit is operative to generate a small reset pulse to compensate for temperature and the supply signal variation effect.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]The present invention relates generally to power supply circuitry and, more particularly, to power-on resets for power supply circuitry.[0003]2. Description of Related Art[0004]Traditionally, an electronic device has required a power supply that provides a relatively constant voltage to the electronic device. In such devices, when power is initially applied to the electronic device, a supply signal increases non-instantaneously from a ground potential to an operational level. When the supply signal exceeds a threshold, a “power-on reset” signal indicates to the various components that sufficient voltage is available on the supply signal. The various components of the electronic device may then initialize to a predetermined state in response to the power-on reset signal. In many electronic devices, each time the power-on reset signal is asserted, the electronic device enters the same predetermined state.[0005]Many electr...

AI Technical Summary

Benefits of technology

[0010]Furthermore, the present invention includes a power-on reset circuit that can assert a power-on reset signal of reduced amplitude in response to a decrease in the supply signal when the supply signal has begun its decrease from the operational voltage to a zero or near-zero voltage (associated with a power-down state), and can assert a power-on reset signal of greater amplitude in response to an increase in the supply signal when the supply signal has begun its increase from a zero or near-zero voltage (associated with a power-down state) to the operational voltage.

[0011]The present invention can address the above-stated needs by providing, for example, in accordance with one aspect, a power-on reset circuit in which substantially all of the transistors have a uniform threshold voltage. In another aspect, the power-on reset circuit includes a voltage divider that tracks a supply signal. In accordance with yet another aspect, the power-on reset circuit includes a voltage divider that can provide an ultra-low DC leakage current while tracking the supply signal. According to one aspect of the present invention, a Schmitt trigger circuit can obviate any need for non-uniform threshold voltages by providing, for example, one trigger threshold when recovering from a full power down and another trigger threshold for recovering from a low power state. The Schmitt trigger circuit can further provide another trigger process when transitioning from an operational power to a full power down state. A compensate circuit in accordance with another aspect of the present invention can provide thermal compensation in response to variations in temperature.

Problems solved by technology

When in a low power mode, the supply signal is reduced to a very low level, sufficient to allow some devices to operate but insufficient to allow other components to operate.

Fabricating an integrated circuit with different devices having different threshold voltages can be an expensive and difficult process, possibly requiring multiple mask steps.

Images